The long-term goal is to define the nature of early embryonic growth and tissue specialization processes that play a role in maintaining normal development. Through analyses of specific congenital defects of the limb found in mutant mice or induced by teratogenic drugs, we are searching for any changes in cell proliferation, cell interactions, cell death patterns, and cell differentiation thay may serve as initiating mechanisms in teratogenesis. Pathogenesis and its biochemical correlates will be analyzed in three relatively new mutations in the mouse - namely, cmd/cmd (a model of human dwarfism termed achondrogenesis); Dmm/Dmm (disproportionate micromelia); and Hm(x)/+ hemimelia-extra toe); and in embryos from a series of normal ICR mice exposed to certain teratogenic agents (e.g. retinoic acid, and several antiproliferative drugs) which produce stage-dependent limb malformations. In vitro systems, such as whole embryo, organ, or cell culture, in conjunction with light and electron microscopy (EM) will be used. Growth will be assessed through labeling indices with 3H-thymidine. Tissue interactions will be monitored through developmental behavior of limb buds in vitro in the presence or absence of natural growth factors such as serum, EGF, FGF, and somatomedins. Organ and cell cultures will be used in studies on chondrogenesis. EM, immunocytochemistry, metabolic tracing of radiolabeled precursors, and column chromatography resolving collagen isotypes and proteoglycan molecules will be used to determine the earliest prenatal stage that skeletal blastema express deviations from normal development. Appropriate parallel studies of teratogen-treated and mutant embryos will be conducted. Our studies will clarify the nature of interactions between cells and their microenvironment during organogenesis, and how deviations in the biosynthesis of extracellular matrix macromolecules (collagen and proteoglycans) might affect growth and development in heritable and drug induced embryopathies.